The present invention relates to a nano-gap electrode pair and a method of manufacturing a nano-gap electrode pair. In recent years, an electrode structure (hereinafter referred to as the nano-gap electrode pair) in which a nanoscale gap is formed between opposed electrode parts or formed G0 tips has been a focus of attention. Accordingly, studies are being made actively on electronic devices, biodevices and the like using nano-gap electrode pairs. For example, an analytical apparatus for analyzing the nucleotide sequence of DNA or RNA utilizing a nano-gap electrode pairs has been conceived of in the field of biodevices (see, for example, International Publication No. WO 2011/108540, which is entirely incorporated herein by reference).
In this analytical apparatus, a single DNA or RNA strand is passed through a nanoscale hollow gap (hereinafter referred to as a nano-gap) between electrode parts of a nano-gap electrode pair. Typically single stranded DNA or RNA may be used. Then, currents flowing through electrode parts when bases of a single DNA or RNA strand pass through the nano-gap between the electrode parts are measured, thereby enabling the bases constituting the DNA or RNA strand to be determined on the basis of the values of the currents.
In such an analytical apparatus as mentioned above, the detectable value of a current decreases if the distance between the electrode parts of the nano-gap electrode pair increases. This makes it difficult to analyze samples with high sensitivity. Accordingly, it is desired that the nano-gap between the electrode parts can be formed to be small in size. Accordingly, efforts are being made to develop a nano-gap electrode pair, the distance of which between the electrode parts is short (see, for example, Japanese Patent Laid-Open No. 2006-234799, which is entirely incorporated herein by reference).
Japanese Patent Laid-Open No. 2006-234799, which is entirely incorporated herein by reference, discloses a method for manufacturing a vertical nano-gap on a substrate by creating a three-layer structure comprising a metal layer, a self-assembled monolayer (SAM) or Al2O3 layer, and a metal layer, and then removing the SAM or Al2O3 layer. Japanese Patent Laid-Open No. 2006-234799, which is entirely incorporated herein by reference, also discloses a method for creating a planar nano-gap between a first metal layer and a second metal layer by forming an SAM on a side surface of the first metal layer disposed on a substrate as one electrode part, forming the second metal layer to serve as the other electrode part on the substrate, so as to have contact with the SAM, and then removing the SAM.
Although the distance between the electrode parts can be narrowed in the nano-gap electrode, in some cases, the narrowed distance between the electrode parts may make it more difficult for a single stranded DNA-containing sample solution measurement target to pass through the nano-gap.
Hence, an object of the present invention, which has been accomplished in view of the above-described problem, is to propose a nano-gap electrode pair and a method for manufacturing a nano-gap electrode pair in which a sample fluid can easily pass through a nano-gap between a first electrode part and a second electrode part even if the width of the nano-gap is made to be substantially narrow.